Always use the push functionality when calling the Smart Pixel, because the script is loaded asynchronously to avoid performance issues.

/**
 * @param {function(wtSmart)} fn
 */
wtSmart.push(fn);

Example

window.wtSmart = window.wtSmart || [];
window.wtSmart.push(function(wtSmart) {
    // set initial tracking config
    wtSmart.init.set({
        trackId: '111111111111111',
        trackDomain: 'q3.webtrekk.net'
    });
    
    // set page data
    wtSmart.page.data.set('en.index.home');
    
    // send tracking data and remove data after request
    wtSmart.track();
});